Mono‐ and Bidentate Benzannulated N‐Heterocyclic Germylenes, Stannylenes and Plumbylenes

Abstract

The current state of the chemistry of mono‐ and bidentate N‐heterocyclic germylenes, stannylenes, plumbylenes, and related compounds is reviewed with special emphasis placed on benzannulated derivatives. The preparation, electronic structure, aggregation behaviour, and the coordination chemistry of the free benzannulated carbene analogues and their adducts with Lewis bases and complexes with transition metals are discussed. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

Synthesis of Mixed Tin–Ruthenium and Tin–Germanium–Ruthenium Carbonyl Clusters from [Ru3(CO)12] and Diaminometalenes (M = Sn, Ge)

“…The transition-metal chemistry of heavier analogues of cyclic and acyclic diaminocarbenes, i.e., group-14 diaminometalenes [M(NR 2 ) 2 ; M = Si, Ge, Sn, or Pb], has been slowly but increasingly developed [1][2][3][4] since the seminal discovery by Lappert in 1974 of the first specimens of this family, M(HMDS) 2 [M = Ge, Sn, Pb; HMDS = N(SiMe 3 ) 2 ].…”

Parent Heavy Methylenes: Chemical Tricks to Access Isolable Complexes of Elusive H2E: Species (E=Ge and Sn)

“…[5] In fact, there are numerous examples of both dimetallenes being used to generate two equivalents of the corresponding heavy carbene analogue and the generation of dimetallenes by facile dimerization of metastable heavy carbene species. [5] Naturally the relative stabilities of I and II are controlled by the steric and electronic properties of the substituents at the Group 14 atom E; additionally, the tendency of II to undergo facile dimerization is indicated by its singlet-triplet energy gap.…”

“…[5] In fact, there are numerous examples of both dimetallenes being used to generate two equivalents of the corresponding heavy carbene analogue and the generation of dimetallenes by facile dimerization of metastable heavy carbene species. [5] Naturally the relative stabilities of I and II are controlled by the steric and electronic properties of the substituents at the Group 14 atom E; additionally, the tendency of II to undergo facile dimerization is indicated by its singlet-triplet energy gap. [1] In both cases, sterically congested substituents kinetically stabilize these reactive species, but in the latter case electronic stabilization plays a particularly important role, as shown by p-donor substituents that are capable of stabilizing an empty valence p orbital at the metal center.…”

“…These bands were assigned by calculations and deuterium-labeling experiments. The divalent metal atoms E of these complexes are tetrahedrally surrounded and connected to one NHC and one W(CO) 5 or BH 3 moiety. On the basis of bond lengths in 5 and DFT calculations of model compounds, the complexes are concluded to consist of a dative E !…”

“…[1] In both cases, sterically congested substituents kinetically stabilize these reactive species, but in the latter case electronic stabilization plays a particularly important role, as shown by p-donor substituents that are capable of stabilizing an empty valence p orbital at the metal center. [5] Despite the considerable research in this area, the parent heavy methylenes EH 2 have remained unattainable, because the hydrogen atoms can satisfy neither the steric nor the electronic requirements. However, stabilization can also be achieved with external electron donors (Lewis bases) and acceptors (Lewis acids).…”